Lucky Mobile, maybe? Feeds off Bell towers, says it's no contract/prepaid, but has monthly (30 day) data plan add ons, for up to 8GB - fees vary. Check the website.
https://www.luckymobile.ca/I just found them this morning. I will be checking them out, as they say there are "no data overages" charges. They warn you via SMS when you're getting close to monthly/plan limit, and let you decide how to proceed, add more GB or whatever. Sounds (almost) like an unlimited plan in Canada, at least according to them. :C